Single-crystal neutron diffuse scattering and Monte Carlo study of the relaxor ferroelectric PbZn1/3Nb2/3O3(PZN)

Full three-dimensional diffuse neutron scattering data have been recorded from a single crystal of Pb(Zn1/3Nb2/3) O-3 (PZN) at 300 Kusing the time-of-flight Laue technique on the SXD single-crystal instrument at ISIS. The data show a series of diffuse rods of scattering oriented parallel to each of the six [110] crystal directions. Monte Carlo simulation has been used to demonstrate that the diffuse rods are caused by planar nanodomains oriented normal to the [110] directions. Within these domains, there are correlated displacements of the atoms away from their average site positions. In order to explain the systematic absence of some rods of scattering in the ( h k 1) data but the presence of all rods in the ( h k 0) data, it is necessary that the displacement of an O atom is of opposite sign to that of its neighbouring Pb atoms. This is explained in terms of a model based on the fact that Pb2+ possesses a lone pair of electrons, giving the Pb ion directionality.